1. The Field of the Invention
The present invention relates to tissue cassette assemblies and methods of use.
2. The Relevant Technology
To accurately diagnose a diseased tissue sample, the tissue sample is first processed to remove the water content. Next, the tissue sample is embedded in paraffin wax, following which a microtome is used to cut thin slices of the tissue. A pathologist is then able to analyze the thin slices to diagnose the disease.
Tissue cassettes are commonly used in the processing step to assist in the removal of the water content from the tissue sample. Tissue cassettes come in a variety of different configurations and can be used in different methods. In one embodiment, the tissue cassette includes a base having a compartment for receiving a tissue sample and a lid that selectively covers the compartment to capture the specimen therein. A pair of sponges may be used within the cassette to sandwich in and prevent small specimen loss during tissue processing steps and/or to sandwich the tissue sample in a desired orientation. The pair of sponges may be omitted if the appropriate specimen size warrants.
With the tissue sample loaded in the tissue cassette, the compartment of the tissue cassette is sequentially flooded with a series of different solvents to remove the water content from the tissue sample. The tissue cassette has relatively large openings in both the lid and base that permit the solvents to freely flow into and out of the compartment for treating the tissue sample. Once the water content has been removed from the tissue sample, the tissue cassette is opened and the sponge(s) are removed and discarded. The tissue sample is placed into a separate mold and the cassette base is coupled to the mold. Liquid paraffin wax is then poured onto the tissue cassette so that the paraffin wax passes through the openings in the lid and the base so as to surround and enclose the tissue sample. The mold holding the tissue cassette acts as a cup to receive and hold the paraffin wax as it solidifies around the tissue sample. Once the paraffin wax has solidified, the frame is then used to mount the embedded tissue sample onto the microtome following which the desired slices can be obtained.
Although the above tissue cassette is functional for processing tissue samples, it has a number of shortcomings. For example, the sponges used for holding the tissue sample are not intended to become part of the final paraffin block-tissue-sample-cassette base assembly; they are intended to be discarded after processing and before embedding with molten paraffin. As such, the specifications of the sponge are not tightly held and vary widely. That is, the pore size, the density, the air-flow volume, and other parameters are not required to be held into a tight range of parameters. The sponge is non-reticulated, that is, a closed cell sponge, and is designed to sufficiently aid in the flow of tissue processing reagents during the tissue processing step, but is not intended to hold a tissue specimen in its final orientation within a paraffin block. It is assumed that a trained technologist re-orients all tissues into the final orientation at the embedding step. Because the parameters of this sponge are not required to be tightly held, fragments of the sponge can and do fragment and become lodged into the tissue sample, creating artificial sponge artifact on the slide. In addition, the sponge, with little resistance to pressure forced onto it by a tissue sample, can imprint its shape onto the tissue surface, introducing another form of artifact. Both forms of sponge artifact can and do create difficulty in proper sample analysis. During the processing stage, the tissue sample is sequentially exposed to a series of different reagents. As a result of the sponge retaining a reagent, the retained first reagent can contaminate the second reagent and make it less effective. More frequent reagent changes/reagent refreshing are required when using a pair of sponges.
Finally, as discussed above, the prior art requires that the tissue cassette be used with a separate frame and mold to enable embedding with paraffin wax and securing to the microtome. The required use of these additional parts increases the expense and slows the processing time. Accordingly, what are needed are systems and methods that address some or all of the above shortcomings and other deficiencies known in the art.